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I've lost (due to the manifold painting) all my marks previously made.
I've timed my engine to number one TDC, but now, I'm searching where is the cylinder one tower on distributor, because GM had forgotten to mark this on plastic...
My engine was so before demounting :
If I take the picture on the AIM 1972, this is correct, so far I can see :
BUT, I read this on service manual (always 1972) :
No. 1 spark plug wire is installed in the first distributor cap tower after the adjusting window, moving in the direction of rotation.
The picture in the manual is too small to show here, but the position of the number one is clearly NOT in the same location as in the AIM !
It is in the same location as descripted on manual text.
Has someone other sources to show where this no. 1 must be placed ? It is perhaps not so important as long as the rotor is well oriented to no. 1 tower ?
Hi Chris,
Because of the placement of the right side distributor shield support the distributor on Corvette engines was clocked differently than distributors of engines headed for steel body cars.
The distributor is clocked so the advance can is to the rear of the support bracket.
Notice where 'Forward' is in View B.
Regards,
Alan
I believe this is the typical location for the #1 plug.
Which is also your number one, assuming this is your engine in the pic. BUT-where number 1 wire is is not so important as where the distributor rotor is when at TDC after compression strike. It either needs to be reset to the correct location or move plug wires so that 1 lines up with rotor. Oil fill in right valve cover is right over cyl 6. So when you see both of those rockers moving as mark goes by tdc, you know you are on fire point for 1.
I've always thought that the TDC after compression is when the 2 rockers arms on cyl 1 are "flat", without any stress on them. In one valve is compressed, this means your 360° off.
This is the procedure descripted on Haynes-book Chevrolet Engine Overhaul Manual.
But I can also check with rockers position on cyl 6 to be sure.
No. Close. When 1 or other rocker is open, it is somewhere close to 90 to 180 crank degrees out. When both rockers are moving at the same time, engine is 360 degrees, out. At tdc, but the other cyl also at tdc is firing. In #1's case it is 6. That is why you can use #6 rockers to tell if 1 or 6 is supposed to be firing.
For what it is worth...in case you were unaware of it.
Or use another method that has been used for long time by mechanics.
IF a person uses this method they are doing so at their own discretion and I am NOT liable for any consequences. I can not help that there are idiots out there in the world. And I AM NOT referring to or implying that anyone here in this thread is an idiot. Just so we are clear on that.
I simply remove the number one spark plug and put my finger over the hole and spin or bump the engine in short bursts until I feel compression and then rotate the engine according to get notch to line up withe the '0' on the timing tab.
AND...I also kill power to the coil or distributor so I do not actually get the engine to fire up when I am doing this.
Now I have no problem doing it this way and it does no bother me that my finger gets blown off the spark plug hole. Which is why I bump the starter to spin the engine. But those people who are fearful, intimidated or fragile or 'whatever' ...then do not do it..
I have never got hurt doing it this way...and if a person does this and does get hurt. Then I do not know what to say and that person may also be the person who gets a paper cut when opening up a letter.
OR...they can buy the tool that sounds off when the compression stroke is achieved.
For what it is worth...in case you were unaware of it.
Or use another method that has been used for long time by mechanics.
IF a person uses this method they are doing so at their own discretion and I am NOT liable for any consequences. I can not help that there are idiots out there in the world. And I AM NOT referring to or implying that anyone here in this thread is an idiot. Just so we are clear on that.
I simply remove the number one spark plug and put my finger over the hole and spin or bump the engine in short bursts until I feel compression and then rotate the engine according to get notch to line up withe the '0' on the timing tab.
AND...I also kill power to the coil or distributor so I do not actually get the engine to fire up when I am doing this.
Now I have no problem doing it this way and it does no bother me that my finger gets blown off the spark plug hole. Which is why I bump the starter to spin the engine. But those people who are fearful, intimidated or fragile or 'whatever' ...then do not do it..
I have never got hurt doing it this way...and if a person does this and does get hurt. Then I do not know what to say and that person may also be the person who gets a paper cut when opening up a letter.
OR...they can buy the tool that sounds off when the compression stroke is achieved.
DUB
I too use the old school finger method. I even used it when working on small aircraft engines. It's infallible but I understand people getting squeamish doing it this way. Once you feel the compression and get the piston all the way to TDC then the post the rotor is pointing will become #1. Then just wire the rest to the firing order. 1-8-4-3-6-5-7-2. If your car has a tach drive distributor you should really clock it so there is the least amount of strain or bend on the tach drive cable.
As Dub said just make sure you remove power from the coil. I usually remove the coil HT off completely and put it on my tool box. I also usually have the cap off to watch the rotor turn as well (just something I like to see).
This method does require a remote starter switch or a partner in the car that knows what he/she's doing or really long arms.
I've this Morning taken pictures from rockers on cyl. 1 and 6 :
I've also checked the rockers : on no.1, both are completely loose and on 6 both are "fixed". all other cylinders have one or another loose or fix, respectively.
Regarding to what is written in the book, this position is correct. Any advice ?
This doesn't help the OP, but my distributor r&r is simple. Every V8 distributor I r&r, I mark the cap for #1 wire and rotate the engine so the rotor points forward and also note the direction the vacuum can (or wire harness if no vacuum can) points. Lift out the distributor and paint pen a stripe on the distributor body to where the rotor now points. When reinstalling the distributor, line up the rotor with the paint stripe, and drop in. If the rotor points forward, it is in correctly. This assumes the engine was not rotated after removal.
I've this Morning taken pictures from rockers on cyl. 1 and 6 :
I've also checked the rockers : on no.1, both are completely loose and on 6 both are "fixed". all other cylinders have one or another loose or fix, respectively.
Regarding to what is written in the book, this position is correct. Any advice ?
'Melwff' I did not read your link due to I know how to do this..so if I repeat any part of it...that is why.
And unless I am having complete brain fart...someone correct me if I am wrong on this.
But the photos that have been recently posted mean nothing at all due to not knowing what was going on it get it to that point that the photo was taken.
Point being...there is a point when BOTH number one and number six pistons are at the top of the stroke. And NOT knowing how the rocker arms were moving...there is no way in knowing if number one cylinder is on the compression stroke or not.
SO..watching the number one INTAKE rocker arm is important. Because...when the number one intake rocker arm is pushing DOWM on the valve springs it is letting in the air/fuel mix into the cylinder because the piston is going down and drawing it in for maximum volume of air/fuel mix.
Then the intake valve will begin to close and the rocker arm goes UP. When it is UP. NOW that cylinder is closed off and the piston can come up more and begin to compress the air/fuel mix so it can be ignited. SO....you rotate the crank and get the notch in the balance to line up to '0" on the timing tab and in doing so...the exhaust rocker arm is NOT trying to open the valve and push down on the valve spring.
IF you keep turning the crankshaft....the exhaust rocker arm will begin to go down and the piston is now coming back up and pushing out the exhaust gases that just occurred when the cylinder fired.
'Melwff' I did not read your link due to I know how to do this..so if I repeat any part of it...that is why.
And unless I am having complete brain fart...someone correct me if I am wrong on this.
But the photos that have been recently posted mean nothing at all due to not knowing what was going on it get it to that point that the photo was taken.
Point being...there is a point when BOTH number one and number six pistons are at the top of the stroke. And NOT knowing how the rocker arms were moving...there is no way in knowing if number one cylinder is on the compression stroke or not.
SO..watching the number one INTAKE rocker arm is important. Because...when the number one intake rocker arm is pushing DOWM on the valve springs it is letting in the air/fuel mix into the cylinder because the piston is going down and drawing it in for maximum volume of air/fuel mix.
Then the intake valve will begin to close and the rocker arm goes UP. When it is UP. NOW that cylinder is closed off and the piston can come up more and begin to compress the air/fuel mix so it can be ignited. SO....you rotate the crank and get the notch in the balance to line up to '0" on the timing tab and in doing so...the exhaust rocker arm is NOT trying to open the valve and push down on the valve spring.
IF you keep turning the crankshaft....the exhaust rocker arm will begin to go down and the piston is now coming back up and pushing out the exhaust gases that just occurred when the cylinder fired.
DUB
I did not quote you, I quoted the OP, I am quite aware you know what you are doing, thanks.
I understand there are several ways to check if you're on correct position with cyl. 1 !
Regarding the instruction sheet on Post 2 (yes, I read it and even print it because it's very interesting !) , I'm unable to check the compression with the starter motor for now because not all electrical devices are connected for now and also because it seems to be quite dangerous to do this...
I'll check today the valves movement (via rockers arms) to be sure I'm really on compression cycle.
I recently did it this way after removing the distributor and replacing the tach cable.
When the compression pushes your finger off the plug hole there's no mistakes your on the compression stroke. Boy 10.25 to 1 feels good.
Marshal
Look at rockers on #6 while bumping the engine over. You will see the #6 exhaust rocker closing. Just as the intake starts to open while exh is closing, stop bumping engine. Now look at timing mark. Probably right on tdc or real close. At this point you know you are firing on 1 cuz you know 6 is between exh and intake strokes. It is not rocket science. Even an idiot like me can figure this out.
Last edited by derekderek; 05-11-2018 at 05:33 PM.
He can not bump the engine with the starter... as like he wrote in POST #15. Because I know that bumping the engine over is usually done with the starter and not my manually spinning it....but I may be wrong on t hat.
You can still find the compression stroke with your finger by turning the engine with a socket and breaker bar. It just takes a little longer if for instance #1 is just coming out of the top of it's compression stroke and traveling down (you'll actually feel a suction) if that's the case it will take a few turns of the crank to get #1 back on it's compression stroke. I've found #1 TDC this way many times.
Yesterday, I've mounted my distributor after a last check : I've rotated my engine one full turn to see the rockers position and one another full turn to return on original position.
I've seen there is one thing to watch out during this mounting : the positions of the vacuum advance capsule and the cable of mechanical tach drive can interfere with the ignition shield brackets !
This could, in my opinion,prevent the rotation of the distributor and therefore, not allow an adjust of the ignition point.
05-09-2018, 12:34 PM
Position cylinder n°1 on distributor
